We have been developing a stereo camera whose field of view is 360 degrees consisting of three hyperbolic mirrors and a single camera, which makes this camera compact and inexpensive. The hyperbolic mirrors enable the omnidirectional view and combining three of them makes it possible to obtain images from two different viewpoints, which are used to measure distances based on the stereo vision principle. By adopting a radiation-tolerant camera (250 kilo pixels) as the single camera, this stereo camera becomes a sensing device suitable for robot operation in harsh radiation environments. The prototype measures approximately 360 millimeters in height and achieves a distance measurement error of less than 5% for objects 1.5 meters apart.
Compact and low-cost devices are needed for autonomous driving to image and measure distances to objects 360-degree around. We have been developing an omnidirectional stereo camera exploiting two hyperbolic mirrors and a single set of a lens and sensor, which makes this camera cost efficient. This paper presents a new calibration method for this camera. Based on the original calibration method by Mei and Rives, we improve the calibration accuracy by considering higherorder radial distortion, detailed tangential distortion, an image sensor tilt, and a lens-mirror offset. Our method is applied to our prototype and reduces the root mean square of the calibration accuracy by 1.2 times and 2.2 times for the upper- and lower-view images, respectively. The distance error is less than 8% up to objects 14 meters apart, which is improved more than seven times compared to the original method, although the error is still larger than the target value of 5%. We consider that the remaining calibration error is due to distortion of the glass cylinder and a degraded optical resolution. As future work, we plan to make further improvements in the calibration and optical resolution of the prototype. In addition, a rectification method for cylindrically expanded images needs to be developed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.